Fluid flow control apparatus

ABSTRACT

A fluid flow apparatus which will permit a varying quantity of fluid to be bled from a main fluid supply without substantially affecting the rate of flow of the main fluid supply.

Johnson et al. Sept. 4, R973 [54] FLUID FLOW CONTROL APPARATUS 3,674,0447/1972 Mayer l37/8L5 3,621,655 111971 11 1 781. x [751 Inventors: LinleyJohns, 3,665,947 5/1972 M1312: l 37/8 L5 -T Hugh Francis 3,592,3097/1971 Joby l37/8l.5 Cantwell, Lmleov r, both f 3,592,213 7/1971Smith... 137 81.5 x England 3,598,137 8 1971 01316.... 137/8l.53,638,672 2 1972 Smith etal l37/8l.5 [73] Asslgnee: The secretaryDefence 3,643,428 2/1972 Marshall et 31.... 137/8l.5 x London, England3,674,045 7/1972 Millman etal 137 81.5

[22] Filed: Oct. 14, 1971 [21] Appl. No.: 189,235 Primary E,1: qrninerSamuel Scott Attorney- Cushman, Darby, Lloyd J. Street et al.

[30] Foreign Application Priority Data I 06:. 22, 1970 Great Britain50,185 70 [57] ABSTRACT [52] us. Cl. 137/810, 137/812 [51] ll!- Cl. Aflow apparatus which permit a varying [58] Fleld of Search l37/8l.5uantity of fluid to be bled from a main fluid supply withoutsubstantially affecting the rate of flow of the [.56] Refe e ce Citedmain fluid supply.

UNITED STATES PATENTS 3,473,545 10 1969 Boyadijieff l37/81.5 10 Claims,2 Drawing Figures FLUID'IFLUW CONTROL APPARATUS This invention relatesto fluid flow control apparatus and is particularly, although notexclusively, suitable for use in the fuel control system of a gasturbine engme.

It is often the practice in a gas turbine engine to bleed fuel from themain fuel supply to the engine and use it to operate various engineancillaries such as servos, hydraulic motors and the like.

Such ancillaries are not in use constantly and thus the demand for fuelto operate ancillaries varies. Hence the amount of fuel bled from themain supply must also be varied. This causes a fluctuating demand forfuel upstream of the bleed point which must be compensated for byadjustments in the delivery rate of the fuel pump, either by alterationsin speed, stroke, or spill rate dependent upon the type of pump used.

If the change in demand for fuel in the main supply is rather rapid thepump may not be able to change its delivery rate quickly enough due tothe lag inherent in some types of pump and, if the demand for fuel bythe ancillaries increases rapidly it is possible for the main fuelsupply to the engine to be reduced temporarily until the pump output hasbeen suitably increased.

It is the object of the present invention to provide a fluid flowapparatus which will permit a varying quantity of fluid to be bled froma main fluid supply without substantially affecting the main fluidsupply.

According to the present invention fluid flow control apparatuscomprises duct means adapted to communicate with a main fluid supplyline, a discharge duct communicating with the duct means, a bleed ductin communication with the duct means and control means adapted tocontrol the proportions of fluid flowing to the discharge duct and tothe bleed duct in accordance with the pressure in the discharge ductwhereby the rate of flow of fluid along the bleed duct is increased andthe rate of flow of fluid along the discharge duct is decreased as thepressure in the discharge duct increases.

Preferably the bleed duct communicates with the duct means upstream ofthe communication between the discharge duct and the duct means.

Preferably the control means comprises a vortex valve (as hereinafterdefined) arranged to communicate with both the duct means and the bleedduct.

Preferably the vortex valve has at least one tangential port connectedto the duct means, and a central port which is connected to the bleedduct.

Preferably the vortex valve has two tangential ports which are mutuallyopposed and are connected to the duct means although the vortex valvemay have one tangential port and one radial port, both being con nectedto the duct means, the tangential port being connected to the duct meansupstream of the radial port.

Preferably the two tangential ports of the tangential and the radialport are connected to the duct means one each side of a restrictorarranged in the duct means.

A further restrictor may be located between the duct means and the portconnected to the duct means upstream of the restrictor.

In this specification the term vortex is applied to a cylindricalchamber having at least one port in the circumferential wall of thechamber, and a port substantially in the centre of the end wall of thechamber and means for preventing or promoting the occurence of a vortexin the cylindrical chamber.

Embodiments of the invention will now be described by way of exampleonly with reference to the accompanying drawings in which;

FIG. 1 illustrates diagrammatically a fluid control apparatus inaccordance with the invention and,

FIG. 2 illustrates an alternative arrangement to the one shown in FIG.1.

Referring to FIG. 1 a main fluid supply duct 1, which may for example bethe main fuel supply line in a gas turbine engine, is provided with anofftake duct 2 which, via a connecting duct 4, supplies a discharge duct3 which leads to a servo system for operating the gas turbine engineexhaust nozzle represented by m.

It will be seen that the rate of flow of fuel Q through the dischargeduct 3 and the pressure existing in the discharge duct 3 will bedependent upon the setting of A restrictor n is located in theconnecting duct 4, and a further restrictor n is located in thedischarge duct 3.

A vortex valve 5 which comprises a cylindrical chamber is connected tothe offtake duct 2 via a duct 6 and to the connecting duct 4 via a duct7.

The ducts 6 and 7 are connected to the vortex valve 5 tangentially intothe circumferential wall of the vortex valve. A bleed duct 8 leads fromthe centre of one end wall of the vortex valve and is led to a lowpressure portion of the fuel system. A restrictor n is located in theduct 6.

The arrangement is such and the restrictors n n and n and the tangentialport restrictions into the vortex valve 5 are sized so that when is atthe minimum flow required the pressures Poll and Pc2 in the ducts 6 and7 will be equal. The rates of flow of fuel Q and Q, in the ducts 6 and 7will thus be equal and the fuel will flow straight through the vortexvalve 5 and into the bleed duct 8.

As the rate of flow O in the discharge duct 3 is increased above itsminimum value the pressure Pc2 in duct 7 will fall relative to thepressure Pcl in duct 6 and the fuel will now enter the vortex chamber 5tangentially, so creating a vortex in the chamber. The flow to the bleedduct 8 and the flow Q, will be reduced, the vortex valve gaincharacteristic being arranged so that the reduction in 0,, will matchthe reduction in Q2 (and any change in the flow Q in duct 6). The totalrate of flow of fuel Q through the offtake duct will thus remainsubstantially constant.

In reverse, as the demand for fuel reduces, thus reducing 0:, thepressure Pc2 increases, the vortex valve is reduced and the flow throughthe vortex valve increases thus increasing 0;.

Another embodiment of the invention is shown in FIG. 2.

The method of operation is similar but the duct 7 is replaced by aradial duct 7a. Again as Q increases the pressure Pc2 in the duct 7atends to drop and a greater pressure differential exists between Pcl andP02. The vortex strength in the vortex valve 5 increases and Q, reduces.

If it is important that the ducts 4 and 3 should be supplied withminimum pressure loss orifices, the restrictors n and a could bereplaced by a venturi with the duct 7 or tapped from the throat of theventuri.

The restrictor n is not essential but is provided to limit the maximumflow O to a value at which the apparatus still function correctly.

Whilst the apparatus has been described in connection with the fuelcontrol system of a gas turbine engine it is, of course, suitable forany apparatus in which it is required to bleed a varying quantity offluid from a fluid supply line without substantially affecting the flowthrough the fluid supply line.

We claim:

1. Fluid flow control apparatus comprising:

a main fluid supply line;

duct means;

means connecting said duct means directly to said main fluid supplyline;

a discharge duct;

means connecting said discharge duct directly to said duct means;

a bleed duct;

means connecting said bleed duct to said duct means;

said main fluid supply line and said duct means carrying a continuousflow of fluid to said discharge duct and said bleed duct when theapparatus is in use; and

control means, said control means being arranged to control the rate offlow of fluid flowing through said bleed duct from said continuous flowthrough said duct means in accordance with pressure in said dischargeduct whereby the rate of flow of fluid in said bleed duct is increasedand the rate of flow of fluid in said discharge duct decreases as saidpressure in said discharge duct increases, and the rate of flow of fluidin said bleed duct is decreased and the rate of flow of fluid in saiddischarge duct increases as said pressure in said discharge ductdecreases.

2. Fluid flow control apparatus as claimed in claim 1 wherein said bleedduct is connected to said duct means upstream of the connection betweensaid discharge duct and said duct means.

3. Fluid flow control apparatus as claimed in claim 2 wherein saidcontrol means comprises a vortex valve, means connecting said vortexvalve with both said duct means and said bleed duct.

4. Fluid flow control apparatus as claimed in claim 3 wherein saidvortex valve has at least one tangential port and means connecting saidat least one tangential port to said duct means, and said vortex valvehas a central port and means connecting said centrol port to said bleedduct.

5. Fluid flow control apparatus as claimed in claim 4 wherein saidvortex valve has two tangential ports which are mutually opposed andmeans connecting said two tangential ports to said duct means.

6. Fluid flow control apparatus as claimed in claim 5 wherein said twotangential ports are connected to said duct means one on each side of arestrictor arranged in said duct means.

7. Fluid flow control apparatus as claimed in claim 6 wherein a furtherrestrictor is located between the said duct means and said tangentialport connected to said duct means upstream of said flrstmentionedrestrictor.

8. Fluid flow control apparatus as claimed in claim 4 wherein saidvortex valve has one tangential port and one radial port and meansconnecting both said ports to said duct means, said tangential portbeing connected to said duct means upstream of said radial port.

9. Fluid flow control apparatus as claimed in claim 8 wherein saidtangential port and said radial port are connected to said duct meansone on each side of a re strictor arranged in said duct means.

10. Fluid flow control apparatus as claimed in claim 9 wherein a furtherrestrictor is located between said duct means and said tangential port.

# t I t

1. Fluid flow control apparatus comprising: a main fluid supply line;duct means; means connecting said duct means directly to said main fluidsupply line; a discharge duct; means connecting said discharge ductdirectly to said duct means; a bleed duct; means connecting said bleedduct to said duct means; said main fluid supply line and said duct meanscarrying a continuous flow of fluid to said discharge duct and saidbleed duct when the apparatus is in use; and control means, said controlmeans being arranged to control the rate of flow of fluid flowingthrough said bleed duct from said continuous flow through said ductmeans in accordance with pressure in said discharge duct whereby therate of flow of fluid in said bleed duct is increased and the rate offlow of fluid in said discharge duct decreases as said pressure in saiddischarge duct increases, and the rate of flow of fluid in said bleedduct is decreased and the rate of flow of fluid in said discharge ductincreases as said pressure in said discharge duct decreases.
 2. Fluidflow control apparatus as claimed in claim 1 wherein said bleed duct isconnected to said duct means upstream of the connection between saiddischarge duct and said duct means.
 3. Fluid flow control apparatus asclaimed in claim 2 wherein said control means comprises a vortex valve,means connecting said vortex valve with both said duct means and saidbleed duct.
 4. Fluid flow control apparatus as claimed in claim 3wherein said vortex valve has at least one tangential port and meansconnecting said at least one tangential port to said duct means, andsaid vortex valve has a central port and means connecting said centrolport to said bleed duct.
 5. Fluid flow control apparatus as claimed inclaim 4 wherein said vortex valve has two tangential ports which aremutually opposed and means connecting said two tangential ports to saidduct means.
 6. Fluid flow control apparatus as claimed in claim 5wherein said two tangential ports are connected to said duct means oneon each side of a restrictor arranged in said duct means.
 7. Fluid flowcontrol apparatus as claimed in claim 6 wherein a further restrictor islocated between the said duct means and said tangential port connectedto said duct means upstream of said firstmentioned restrictor.
 8. Fluidflow control apparatus as claimed in claim 4 wherein said vortex valvehas one tangential port and one radial port and means connecting bothsaid ports to said duct means, said tangential port being connected tosaid duct means upstream of said radial port.
 9. Fluid flow controlapparatus as claimed in claim 8 wherein said tangential port and saidradial port are connected to said duct means one on each side of arestrictor arranged in said duct means.
 10. Fluid flow control apparatusas claimed in claim 9 wherein a further restrictor is located betweensaid duct means and said tangential port.